Ashless type engine oil composition

ABSTRACT

Disclosed is an ashless-type engine oil composition. The engine oil composition particularly includes glyceryl monooleate, molybdenum dithiocarbamate and a dihydrocarbyl dithiophosphate metal salt together as a friction modifier. Accordingly, the engine oil composition of the present invention provides advantages of protecting a filter equipped in an exhaust gas after-treatment device and improving gas mileage and engine durability by maintaining sulfated ash in an amount of 0.8 wt % or less based on total weight of the engine oil composition.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119(a) the benefit of Korean Patent Application No. 10-2014-0015485 filed Feb. 11, 2014, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an ashless-type engine oil composition. Particularly, the engine oil composition may include: glyceryl monooleate, molybdenum dithiocarbamate and a dihydrocarbyl dithiophosphate metal salt together as a friction modifier, thereby protecting a filter equipped in an exhaust gas after-treatment device and improving gas mileage and engine durability by maintaining sulfated ash in an amount of about 0.8 wt % or less.

BACKGROUND

An engine oil is a type of lubricant used in an internal combustion engine of a vehicle, and such a lubricant has typically been formed with a base oil and additives. The base oil included in a lubricant is generally categorized into Group Ito Group V according to the mineral base oil standard defined by the American Petroleum Institute (API). The base oils of the Groups I, II and III are mineral oil-based base oils, and are further categorized depending on the degree of saturation, viscosity index and the content of sulfur. The base oil of the Group IV is a synthetic-based base oil or polyalphaolefin (PAO). The base oil of the Group V refers to the base oil that is not included in Group Ito Group IV, and includes an ester.

In general, the engine oil circulates through an oil tank, an oil strainer, an oil pump, an oil filter, an oil cooler, a metal friction surface and the oil tank. Particularly, the engine oil may reduce the friction and the abrasion in various apparatuses generated by the operation of the engine, and thereby enables the engine to operate smoothly. For example, the engine typically includes a part in rectilinear motion, such as cylinder and piston operations, and also includes a part in rotary motion, such as a crankshaft and a camshaft. When the metal parts generating kinetic friction as described above are in contact with each other, friction heat is also generated due to the kinetic friction, and the friction surface on which the kinetic friction is generated becomes roughened. Accordingly, the roughened friction surface may lead to easy abrasion due to the friction or adhesion due to the frictional heat.

In the related art, the engine oil is injected to the friction surface of a metal to prevent abrasion caused by friction and friction heat, an oil film is formed as the metallic surface is covered by the engine oil. Accordingly, solid friction between metals changes to fluid friction between lubricants by the oil film, and mechanical friction and abrasion between metals are substantially reduced. Furthermore, heat generated in an engine may be dispersed by the engine oil, and thus, the engine oil may contribute to cooling action of the engine. In addition, the engine oil may maintain durability of the engine by a sealing action which prevents the leak of high pressure gas of a cylinder, a cleaning action which absorbs impurities in an engine oil fluid process and cleans the engine, a stress breakup action which disperses pressure and an anti-corrosive action which prevents penetration of moisture or corrosive gas.

In the related art, a dispersant has been used as an additive used in the engine oil to prevent the excessive increase of oil viscosity by blocking the aggregation of impurities. Metal salt-type dispersants have been widely used as such a dispersant, but the metal salt-type dispersants may generate ashes when the engine oil burns.

In addition, as additives used in engine oil, a purifier or detergent have been used to protect an engine by preventing formation of deposits in an engine piston and the like. Materials in a type of metallic soap have been used for such a purifier, and such metallic soap materials are formed with an organic acid and a metal salt. However, the metallic soap-type purifier may generate ashes when engine oil burns.

In accordance with the trend of the engines in vehicles which have been developed with high-powered and minimized features, additional additives have been used in engine oil to strengthen the function described above. However, desired is reducing the amount of additives or using ashless-type additives to protect an exhaust gas filter.

In the related art, the ashless-type engine oil which is capable of protecting an exhaust gas filter may have sulfur content of in an amount of about 0.3 wt % or less, phosphorus content in an amount of about 0.09 wt % or less, and sulfated ash content in an amount of about 0.8 wt % or less in the engine oil. In the conventional ashless-type engine oil as described above, however, the performance of mechanical equipment associated with the engine oil may be reduced due to high density and friction, and when the performance thereof is reduced, gas mileage of the vehicle may decrease.

The above information disclosed in this Background Art section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION

As such, we now provide the present invention to solve the technical difficulties described above by developing an engine oil composition. The engine oil composition in the invention is capable of reducing fluid resistance and friction resistance of ashless-type engine oil, thereby improving gas mileage and durability of the engine parts and protecting an engine exhaust gas filter device.

In one aspect, the present invention provides an ashless-type engine oil composition which may reduce ashes generated when automobile engine oil burns and the ashless-type engine oil composition may contain sulfated ash content in an amount of about 0.8 wt % or less in the engine oil composition.

Particularly, the ashless-type engine oil composition in the present invention may protect an engine exhaust gas after-treatment filter and improve gas mileage by reducing friction resistance of the engine by maintaining sulfated ash content in an amount of about 0.8 wt % or less, phosphorous content in an amount of about 0.09 wt % or less, and sulfur content in an amount of about 0.3 wt % or less, based on the total weight of the engine oil composition of the present invention.

It is understood that weight percents (wt %) of the components as disclosed herein are based on total weight of the engine oil, unless otherwise indicated.

In an exemplary embodiment, the ashless-type engine oil composition may include: a base oil; an ashless dispersant; a metal purifier; a friction modifier, and common engine oil additives. In certain exemplary embodiments, the friction modifier may include glyceryl monooleate, molybdenum dithiocarbamate and a dihydrocarbyl dithiophosphate metal salt, and content of the sulfated ash content in the composition may be in an amount of 0.8 wt % or less.

In yet certain exemplary embodiments, the engine oil composition may protect an engine exhaust gas after-treatment filter since sulfated ash content may be maintained in an amount of about 0.8 wt % or less, phosphorous content in an amount of about 0.09 wt % or less, and sulfur content in an amount of about 0.3 wt % or less, based on total weight of the engine oil.

According to various exemplary embodiments of the present invention, an engine oil composition may improve gas mileage and durability due to reduced friction resistance.

The above and other features of the invention are discussed infra.

DETAILED DESCRIPTION

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about”.

Hereinafter reference will now be made in detail to various exemplary embodiments of the present invention, examples of which are described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

In one aspect, the engine oil composition of the present invention may include (1) base oil, (2) an ashless dispersant, (3) a metal purifier and (4) a friction modifier. Particularly, glyceryl monooleate, molybdenum dithiocarbamate and a dihydrocarbyl dithiophosphate metal salt may be combined to be used as the friction modifier.

Each component of the engine oil composition according to the present invention is described as follows.

(1) Base Oil

In one aspect, the engine oil composition may include a base oil. The base oil, as used herein, may include oils with lubrication viscosity in various ranges or may be one or more natural oils, one or more synthetic oils, or mixtures thereof. The base oil may be included in the composition in an amount of about 50 wt % or greater based on total weight of the engine oil composition. In certain exemplary embodiments, the base oil may be included in a range from about 80 to about 92 wt %, or particularly in a range from about 82 to about 90 wt %, based on total weight of the engine oil composition.

In addition, the base oil may be the natural oil selected from the group consisting of animal oil, vegetable oil, mineral oil and combinations thereof. The mineral oil may be, but is not limited to, liquid petroleum, or, one or more of paraffin-based, naphthene-based and paraffin-based/naphthene-based mixed mineral oils which may be subsequently purified by hydrogenolysis or hydrogenous finishing. Alternatively, solvent-treated or acid-treated mineral oil may be used as the mineral oil.

Further, the base oil may be the synthetic oil. The synthetic oil may be, but is not limited to, hydrocarbon oil such as polymerized and interpolymerized olefin which is also known as polyalphaolefin; halo-substituted hydrocarbon oil; polyphenyl; alkylated diphenyl ether; alkylated diphenyl sulfide; or derivatives, analogues, and homologues thereof. Other exemplary synthetic oils may be esters which may prepared from various alcohols and esters of dicarboxylic acids or esters which may be prepared from C₄ to C₁₅ monocarboxylic acids and polyols or polyol ethers.

The natural oil and the synthetic oil may be purified, not purified or re-purified, without limitation. The term ‘oil that is not purified’, as used herein, refers to an oil capable of being directly obtained from natural or synthetic supply sources without any purification. The term ‘re-purified oil’, as used herein, refers to an oil further treated in one or more purification steps, without limitation, to improve one or more properties. An exemplary re-purified oil may have improved stability and may be produced by hydrogenation and oxidation.

In other certain exemplary embodiments, the base oil may be a Group II oil, a Group III oil, a Group IV oil and a Group V oil which are defined by the American Petroleum Institute (API), or mixtures thereof. It is appreciated that a range of options is provided by YUBASE 3 (SK Corporation, South Korea) for Group II oil and YUBASE 6 (SK Corporation, South Korea) for Group III oil in the present invention. An exemplary Group IV oil may be, but not limited to, polyalphaolefin, and an exemplary Group V oil may be, but is not limited to, esters.

According to various exemplary embodiments, the base oil may be selected from the oils having a single viscosity range and mixtures of oil having a high viscosity range and oil with a low viscosity range.

(2) Ashless Dispersant

In one aspect, the engine oil composition may include an ashless dispersant. The ashless dispersant may be included in an amount of about 3 to 8 wt %, or particularly, in an amount of about 3 to 5 wt % by weight, based on total weight of the engine oil composition. When the content of the ashless dispersant is included in an amount less than about 3 wt %, viscosity and the like may increase since a dispersion effect of foreign substance in the engine oil composition may be significantly reduced. When the ashless dispersant is included in an amount greater than about 8 wt %, dispersion effect may not be sufficiently improved, and a viscosity adjusting effect may be reduced due to substantially high viscosity.

In certain exemplary embodiments, the ashless dispersant may have a reduced ash content and substantially disperse foreign substances such as water and soot in the engine oil. In addition, the ashless dispersant may be, but is not limited to, long chain hydrocarbyl succinimide, long chain hydrocarbyl succinamide, a mixture of long chain hydrocarbyl-substituted succinic acid ester/amide, long chain hydrocarbyl-substituted succinic acid hydroxyester, long chain hydrocarbyl-substituted phenol, Mannich condensation products of formaldehyde and polyamine and the like. Further, mixtures of the ashless dispersant described above may also be used. As used herein, long chain hydrocarbyl group refers to a hydrocarbyl group having a chain of about 10 to 40 carbon atoms.

In other exemplary embodiments, the ashless dispersant may be, but is not limited to, a long chain alkenyl succinimide, which may include non-cyclic long chain hydrocarbyl-substituted succinimide prepared using various amines or amine derivatives in the related art. In addition, the ashless dispersant may be a long chain alkenyl succinimide treated with inorganic acids of phosphorous or anhydrides thereof and boronated agents. The long chain alkenyl succinimide may have substantial compatibility for elastomer seals prepared from substances such as a fluoro-elastomer and a silicon-containing elastomer. As used herein, the long chain alkenyl or the long chain hydrocarbyl group refers to a alkenyl or hydrocarbyl group having a chain of about 10 to 40 carbon atoms.

In particular, the ashless dispersant may include a succinic imide derivative and a succinic amide derivative, which may be obtained by reacting polyamine and alkenyl succinic anhydride, or a mixture thereof. The polyamine may be, but is not limited to, triethylene tetramine, tetraethylene pentamine or a mixture thereof. The alkenyl succinic anhydride may be a succinic anhydride substituted with an alkenyl group having about 2 to 12 carbon atoms and including one or more unsaturated hydrocarbon with double bonds. In addition, fluid resistance, dispersibility and a friction coefficient of the engine oil composition may be adjusted by adjusting the carbon number of the substituted alkenyl forming the ashless dispersant.

According to various exemplary embodiments, the ashless dispersant described above may be used either alone or as a combination without limitation.

(3) Metal Purifier

In one aspect, the engine oil may include a metal purifier. The metal purifier may be included in an amount of about 3 to 6 wt %, or particularly in an amount of about 3 to 5 wt %, based on total weight of the engine oil composition. When the content of the metal purifier is included in an amount of less than about 3 wt %, the effect of deposit removal may be significantly reduced. When the metal purifier is included in an amount greater than about 6 wt %, the purification effect may not increase subsequently, and the exhaust gas after-treatment filter device may be damaged when engine oil burns due to the increase of ashes.

The metal purifier may be a metal salt which may be obtained by reacting alkaline earth metals and organic acids having about 4 to 20 carbon atoms. Exemplary metal purifiers may be, but are not limited to, calcium salicylate, magnesium salicylate and the like as alkaline earth metal salicylate.

(4) Friction Modifier

In one aspect, the engine oil composition may include a friction modifier. The friction modifier may be, but is not limited to, glyceryl monooleate, molybdenum dithiocarbamate or a dihydrocarbyl dithiophosphate metal salt, and a particular exemplary friction modifier may be zinc di(alkyl having 8 to 20 carbon atoms)dithiophosphate, ZnDDP. As used herein, the friction modifier particularly mixed and used together with the metal purifier may reduce fluid resistance and friction resistance of engine oil by the synergic effects obtained from the friction modifier and the metal purifier, thereby providing special effects to improve gas mileage and durability.

In certain exemplary embodiments, the glyceryl monooleate in an amount of about 0.8 to 1.5 wt %, the molybdenum dithiocarbamate in an amount of about 0.4 to 1 wt % and the dihydrocarbyl dithiophosphate metal salt in an amount of about 1 to 2 wt % may be included as a friction modifier based on total weight of the engine oil composition.

When the content of the glyceryl monooleate is included in an amount of less than about 0.8 wt %, the friction reduction effect may be reduced by about half. Meanwhile, when the glyceryl monooleate is included in an amount of greater than about 1.5 wt %, the friction reduction effect may not increase accordingly. When the content of the molybdenum dithiocarbamate is included in an amount of less than about 0.4 wt %, the period maintaining the friction reduction effect may be significantly shortened. When the molybdenum dithiocarbamate is included in an amount of greater than about 1 wt %, the friction reduction effect may not increase accordingly. In addition, when the content of the dihydrocarbyl dithiophosphate metal salt is included in an amount of less than about 1 wt %, the friction reduction effect may be reduced by about half. When the content of the dihydrocarbyl dithiophosphate metal salt is included in an amount of greater than about 2 wt %, the life span of an after-treatment device may be reduced due to the increase of the phosphorous content.

(5) Other Additives

In one aspect, the engine oil composition may independently include various additives commonly used in the art. The additives may be, but are not limited to, a viscosity modifier, an anti-wear agent, an antioxidant, a pour point depressant, a corrosion inhibitor, an antifoaming agent, a dye and the like.

The viscosity modifier, as used herein, may maintain an oil film by preventing the viscosity from decreasing at elevated temperatures, and may be used to reduce oil liquidity and fluid resistance by preventing the viscosity from substantially increasing at substantially low temperatures (e.g., reduced temperatures). Such a viscosity modifier may be, but is not limited to, polymethacrylate, polyacrylate, polyolefin, a styrene-maleic acid anhydride copolymer, and an analogous homopolymer, copolymer or grafted copolymer which may be widely used in the related art. The viscosity modifier may be included in the engine oil composition in an amount of about 1 to 10 wt %, or particularly of about 2 to 5 wt %, based on total weight of the engine oil composition.

The anti-wear agent may be, but is not limited to, a phosphorous-based anti-wear agent which may be widely used in the related arts. In certain exemplary embodiments, the phosphorous-based anti-wear agent may be an organic ester of phosphorous acid or organic-phosphite, or an amine salt of phosphorous acid. The phosphorous-based anti-wear agent may be included in an amount of about 0.05 to 2.0 wt %, or particularly of about 0.1 to 1.0 wt %, based on total weight of the engine oil composition.

The antioxidant may be, but is not limited to, selected from aromatic amine-based and hindered phenol-based compounds which may be widely used in the related arts. In certain exemplary embodiments, the antioxidant may be included in an amount of about 0.05 to 2.0 wt %, or particularly of about 0.1 to 1.0 wt %, based on total weight of the engine oil composition.

The pour point depressant, as used herein, may increase liquidity at reduced temperatures. This pour point depressant may be, but is not limited to, polymethacrylate and the like which may be widely used in the related arts. The pour point depressant may be included in an amount of about 0.05 to 2.0 wt %, or particularly of about 0.1 to 1.0 wt %, based on total weight of the engine oil composition.

The corrosion inhibitor, as used herein, may reduce decomposition of metal components which are in contact with the engine oil composition. The corrosion inhibitor may be, but is not limited to, thiadia and the like which may be widely used in the related arts. In certain exemplary embodiments, the corrosion inhibitor may be included in an amount of about 0.01 to 2.0 wt %, or particularly of about 0.1 to 1.0 wt %, based on total weight of the engine oil composition.

The antifoaming agent, as used herein, may delay the foam formation. The antifoaming agent may be, but is not limited to, silicone oil, an organic silane compound such as polydimethyl siloxane, and an organic polymer which may be widely used in the related arts or may be a commercially available product. In certain exemplary embodiments, the antifoaming agent may be used in reduced quantities combined with other additives such as an anti-emulsifying agent, and may be included in an amount less than about 1 wt %, or particularly less than about 0.01 wt %, based on total weight of the engine oil composition.

In various exemplary embodiments of the present invention, the engine oil composition having composition components and composition ratios as described above may be mixed to have kinematic viscosity of about 5 to 15 cSt, of about 8.0 to 13 cSt, or particularly of about 9.3 to 12.5 cSt at a temperature of about 100° C. When the kinematic viscosity of the engine oil composition is less than a predetermined value, for example, less than about 5 cSt, vehicle gas mileage may decrease due to increase in friction resistance. When the kinematic viscosity is greater than a predetermined value, for example, greater than about 15 cSt, vehicle gas mileage may decrease due to increase in fluid resistance.

In addition, the engine oil composition of the present invention may maintain the sulfated ash content in an amount of about 0.8 wt % or less, the phosphorous content in an amount of about 0.09 wt % or less, and the sulfur content in an amount of about 0.3 wt % or less, based on total weight of the engine oil composition. As consequence, an engine exhaust gas filter may be protected by reducing the generation of ashes when the engine oil burns, and simultaneously, gas mileage may be improved by reducing the friction resistance of the engine.

The present invention will be described in more detail with reference to the following examples, however, the present invention is not limited to these examples.

EXAMPLES

Hereinafter, the present invention is illustrated in various examples, but the aspect of the present invention is not limited to the following examples. All parts and percentages are based on the weight of the engine oil composition unless otherwise specified. Examples represent the engine oil composition according to the present invention.

The engine oil composition was prepared by mixing the components illustrated in the following Table 1 without limitations to the methods in the art.

Materials and Reagents

(1) Base oil: API Group III oil was purchased from SK Corporation

(2) Ashless dispersant: An ashless dispersant obtained by reacting polyalkylene polyamine and alkenyl succinic anhydride which was purchased from Infineum International Ltd (U.S. Pat. No. 3,202,678).

(3) Purifier: Calcium salicylate was purchased from Finetech Industry limited.

(4) Friction modifier:

-   -   {circle around (1)} Glyceryl monooleate was purchased from         Sigma-Aldrich Co.     -   {circle around (2)} Molybdenum dithiocarbamate (MoDTc) was         purchased from Adeka Corporation     -   {circle around (3)} Zinc dihydrocarbyl dithiophosphate (isodecyl         ZnDDP) was purchased from ChemFrog

(5) Other additives

The listed chemical compounds in Table 1 were purchased from Infineum International Ltd.

TABLE 1 Engine Oil Composition (wt %) Example Comparative Examples Category 1 1 2 3 4 5 6 7 Base Oil 83 87 83 84 83 83.7 83 83 Ashless Dispersant 4 4 8 4 4 4 4 2 Purifier 4 0 0 4 4 4 4 6 Friction Glyceryl 1 1 1 0 0 1 1.7 1 Modifier Monooleate MoDTc 0.7 0.7 0.7 0.7 1.7 0 0 0.7 ZnDDP 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 Other Viscosity 4 4 4 4 4 4 4 4 Additives Modifier Anti-wear 1 1 1 1 1 1 1 1 Agent Amine-based 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Antioxidant Pour Point 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Depressant Corrosion 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Inhibitor Antifoaming 100 100 100 100 100 100 100 100 Agent (ppm) Total Sum Content* 100 100 100 100 100 100 100 100 (% by weight) *Total sum content of the total composition components excluding the antifoaming agent. The antifoaming agent is additionally added 100 ppm to the prepared engine oil composition.

In addition, the performance of each prepared engine oil composition was tested according to widely-known performance test methods, and the results are shown in the following Table 2. Furthermore, as a “contrast,” identical tests were performed for commercially available engine oil. The test results are shown in the following Table 2.

TEST EXAMPLES Performance Test Methods

(1) Component analysis

-   -   Phosphorous (P) component analysis: standard ASTM D5185     -   Sulfur (S) component analysis: standard ASTM D5185     -   Calcium (Ca) component analysis: standard ASTM D5185

(2) Sulfated ash test: standard ASTM D874

(3) Friction coefficient test (SRV): standard ASTM D6425

(4) Kinematic viscosity: kinematic viscosity was measured at about 100° C. KV100, according to standard ASTM D-445

(5) Gas mileage (FTP 75 mode): EPA Federal Test Procedure (EPA: US Environmental Protection Agency)

TABLE 2 Physical Property Measurement Results Example Comparative Example Category 1 1 2 3 4 5 6 7 Control Component P 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.09 Analysis (% by S 0.23 0.21 0.25 0.23 0.24 0.21 0.21 0.26 0.3 weight) Ca 0.18 0.06 0.06 0.18 0.18 0.18 0.18 0.234 0.28 Sulfated Ash 0.8 0.7 0.75 0.8 0.8 0.8 0.8 1 1.4 (% by weight) SRV Friction 0.06 0.09 0.09 0.09 0.09 0.1 0.1 0.06 0.09 Coefficient Kinematic 10.5 10.4 10.8 10.5 10.5 10.5 10.8 10.5 10.2 Viscosity (100° C., cSt) Gas Mileage 1.5% 0.5% 0.5% 0.5% 0.5% −0.2% −0.2% −0.2% Reference (FTP 75 mode) Improved Improved Improved Improved Improved Decreased Decreased Decreased

In Example 1, the engine oil composition includes glyceryl monooleate, molybdenum dithiocarbamate and dihydrocarbyldithiophosphate in constant content ratio ranges as a friction modifier. The component analysis results verified that the phosphorous content was maintained in an amount of about 0.09 wt % or less, and the sulfur content was maintained in an amount of about 0.3 wt % or less, and the sulfated ash content was in an amount of about 0.8 wt % or less. Accordingly, the engine exhaust gas filter may be protected by reducing the generation of ashes when engine oil burns. Furthermore, gas mileage may be improved by reducing the friction resistance of an engine.

Meanwhile, the engine oil compositions of Comparative Examples 1 to 6 which do not include several components as the metal purifier or the friction modifier, the effect of gas mileage improvement may not be obtained due to the high friction coefficient. In addition, the engine oil composition in Comparative Example 7 includes calcium salicylate metal purifier in an amount greater than the predetermined amount and the metal purifier in an amount greater than the predetermined amount. However, the friction coefficient may not decrease accordingly, and the composition may not be suitable for gasoline particulate filter (GPF)-equipped vehicles due to the excessive sulfated ash content.

The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. 

What is claimed is:
 1. An ashless-type engine oil composition comprising: a base oil; an ashless dispersant; a metal purifier; a friction modifier; and common engine oil additives, wherein the friction modifier includes glyceryl monooleate, molybdenum dithiocarbamate and a dihydrocarbyl dithiophosphate metal salt; and a sulfated ash content in the engine oil composition is in an amount of about 0.8 wt % or less by weight, based on total weight of the engine oil composition.
 2. The ashless-type engine oil composition of claim 1, wherein the friction modifier includes the glyceryl monooleate in an amount of about 0.8 to 1.5 wt %, the molybdenum dithiocarbamate in an amount of about 0.4 to 1 wt % and the dihydrocarbyl dithiophosphate metal salt in an amount of about 1 to 2 wt %, based on total weight of the engine oil composition.
 3. The ashless-type engine oil composition of claim 1, wherein the dihydrocarbyl dithiophosphate metal salt is zinc di(alkyl having 8 to 20 carbon atoms)dithiophosphate.
 4. The ashless-type engine oil composition of claim 1, comprising: the base oil in an amount of about 80 to 92 wt %; the ashless dispersant in an amount of about 3 to 8 wt %; the alkali earth metal salicylate metal purifier in an amount of about 3 to 6 wt %; the glyceryl monooleate in an amount of about 0.8 to 1.5 wt %; the molybdenum dithiocarbamate in an amount of about 0.4 to 1 wt %; and the dihydrocarbyl dithiophosphate metal salt in an amount of about 1 to 2 wt %, based on total weight of the engine oil composition.
 5. The ashless-type engine oil composition of claim 4, wherein the ashless dispersant is obtained by reacting polyalkylene polyamine and alkenylsuccinic anhydride.
 6. The ashless-type engine oil composition of claim 1, wherein kinematic viscosity of the oil composition at a temperature of about 100° C. is in a range of about 5 to 15 cSt.
 7. The ashless-type engine oil composition of claim 1, wherein phosphorous content is maintained in an amount of about 0.09 wt % or less, and sulfur content is maintained in an amount of about 0.3 wt % or less, based on total weight of the engine oil composition. 